The present invention relates to an analyzer of the kind capable of analyzing a fluid containing at least one substance to be analyzed and at least one inflammable substance, the analyzer containing:
a source of gas to provide a flux of diluent gas,
an injection nozzle for introducing samples of the fluid into the flux of diluent gas and producing a gaseous flux, and
a detector for analyzing the gaseous flux.
The invention also relates to a method for analyzing a fluid containing at least one substance to be analyzed, or an “analyte”, and at least one inflammable substance which can be the analyte or some other substance.
The invention is more particularly adapted to the analysis of fluids presenting a risk of explosion or to an analysis performed in a potentially explosive atmosphere. For example, the invention is adapted to analyses carried out in the petroleum industry, chemistry and petrochemistry.
An explosive atmosphere, or “ATEX”, is a mixture with air, under atmospheric conditions, of inflammable substances, for example in the form of a gas (methane, butane, propane, hydrogen . . . ) or of vapors (carbon disulfide, ethyl alcohol, ethylene oxide, acetone . . . ) in which, after inflammation, the combustion propagates to the unburned mixture.
The fluid to be analyzed can be liquid under the conditions under which it is removed but vaporizes in the diluent gas.
The mixture can become explosive if the concentration of the inflammable substance is above a lower explosivity limit (LEL) which is the minimum concentration of the inflammable substance in the mixture above which the mixture can be ignited. The LEL, often expressed in by volume of the inflammable substance in air, is of the order of 1% or of a few % for many analytes and about 0.5% for the most inflammable ones among them.
In the field of analyzers of the afore-said type, in order to avoid the risk of an explosion, it is known to use a diluent gas virtually free of oxygen, for example nitrogen obtained by cryogenic distillation, or hydrogen, or special mixtures not susceptible to ignite in contact with an analyte. Such a method has the advantage that the inflammation of the mixture of the diluent gas with the fluid to be analyzed is impossible regardless of the nature of the inflammable substance of the fluid to be analyzed or regardless of the mass of the samples of the fluid to be analyzed.
On the other hand, it is necessary to have at one's disposal a source of diluent gas, or gas of dilution, virtually free of oxygen and which in general has a non-negligible unit cost. Moreover, if the diluent gas virtually free of oxygen itself contains an inflammable substance such as hydrogen, the mixture to evacuate at the outlet from the analyzer itself presents a risk of explosion in case of contact with air or more generally with a substance supporting combustion.
One object of the invention is to provide an analyzer very well adapted to fluids containing at least one inflammable substance and that offers a more competitive cost of operation.